PT.. i don't think their going to fit, not unless you plan on stacking the batteries on top of each other,
something i would advise against
you have not given us the compartment dimensions, but your current layout is basically 14"deep by 28~30" wide, that is the foot print of your three grp 29
i see no way to stick (2) batteries laying down, needing a minimum 12"*17" each, that either 24"*17" or 12*34
now if your compartment is tall, maybe you mean stand them on end
then the foot print would be 7*17 each, two batteries on end, one in back one in front 14 deep 17 wide 12 tall